Aircraft Nose-Wheel and Main-Wheel Steering Systems

Steering on the ground is primarily achieved through the nose wheel, but larger aircraft may also employ main-wheel steering. The system is typically hydraulically powered and controlled via a tiller or rudder pedals.

Main-Wheel (Body) Steering

Large aircraft with multiple main gear wheels mounted on bogie beams can experience high sideways loads and tyre scrubbing during tight turns.

• Purpose: to reduce stress on the torsional links and reduce tyre abrasion (scrubbing).
• Operation:
  • It is only used in slow speed tight turns.
  • The main wheels steer in the opposite direction to the nose wheel.
  • It turns sideways forces into longitudinal forces on the main gear assemblies.
  • Benefit: Reduces the turning circle radius.

Nose-Wheel Steering Control

Nose wheel steering is hydraulically powered and activated only when the aircraft is on the ground (controlled by squat switches).

• Control Methods:

  • Hand Wheel Steering (Tiller): Used for low-speed, high-angle turns (e.g., parking). It provides large deflection (typically up to 78 degrees).
  • Rudder Pedals: Used for high-speed steering (e.g., takeoff and landing roll) and minor corrections during taxi. It provides limited deflection (typically up to a maximum of 7 degrees).

• Operational Considerations:

  • Deflection Comparison: Manual/tiller steering offers a significantly larger maximum deflection of the nose wheel compared to rudder pedal steering.
  • Rudder Check: When performing a rudder control check during taxi, an additional pilot action must be taken (disconnecting the steering) to avoid unwanted deflection of the nose wheel, which would cause the aircraft to swerve.
  • In-Flight: Rudder pedal nose-wheel steering does not function in the air.